Ok, not a powerwall. But a Solar powered Raspberry pi

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Peter T

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Apr 6, 2018
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36
Hi all. Found this site after seeing some video on HBPowerwall on Youtube, Great stuff btw. Anyhow my project. So far I have a 40W panel facing SW, Not great but that the only place I can mount it to the outside wall. This 40W panel feed's a cheap PWM solar controller. which is charging a 12V 7Ah Lead acid battery. a MoPi is used to connect the 12V power from the battery to the Raspberry pi. The Mopi is set to shutdown at 11V. Anyhow because I have some old laptop. I've pulled apart the battery's for the 18650. And I need to test them all. But my plan is to replace the 2 year old lead acid battery with the 18650's. So far I have 20 18650's. And i'm not sure to make a 4S4P or a 7S2P, and figure out how I can run it on 24V.
 

daromer

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Oct 8, 2016
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Its generally easier to find a 7s aka 24v powered device but with that said you only need 5v output to your raspi right? if thats the case input voltage only need to suit the buck converter.

Then just add a BMS and you are good to go
 

Peter T

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Apr 6, 2018
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Yep the Pi run's on 5V. The MoPi, bring 12V down to 5V. and it bypass's the usb power for 5V. Now I stated that I have a 40W panel, I do also have a 4w Panel. If I was to make a 24V system would that be ok. Or do I need a second 40W panel.
 

TheBatteries

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PeterT said:
Yep the Pi run's on 5V. The MoPi, bring 12V down to 5V. and it bypass's the usb power for 5V. Now I stated that I have a 40W panel, I do also have a 4w Panel. If I was to make a 24V system would that be ok. Or do I need a second 40W panel.

You need a second 40w panel. The 4w panel won't be able to handle the amps the 40w panel is going to produce.
 

daromer

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Also a 40w panel doesnt give much unless you have blistering sun? :) A raspbery pi do draw some wattage 24/7 so if you want to cover cloudy and rainy days and keep it running during the night i highly recommend a 2nd 40w panel for it.

And a proper MPPT will save you some wattage too. Then as said the voltage on the battery doesnt matter that much since you can use any decent step down converter.
 

Peter T

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Apr 6, 2018
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Well that make sense. two 40W panel, will help load's in the winter. As I try to run the Raspberry pi 2 @ 100% load. That make a nice 24V system, 7S2P for now with 6 18650's spare. 24V to 12V buck converter. I'll just have to work out how to shut the pi down when the voltage drop. i.e for a safe shutdown.
 

daromer

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7s2p will yield some where around 5-15 hours of run time with 2ah batteries (Since i have no clue of what stuff is behind the device :p
 

Peter T

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Apr 6, 2018
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Yep I've now ordered a second 40 watt panel. Like any project it's hmmmmmmm. Can I run that on solar. And the project grows.
 

Peter T

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Apr 6, 2018
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Got the second 40W panel, So 80W in total. Still to build my 7s?p battery. But it running great right now in the Suuny UK. Yes suuny on a bank hoilday weekend. But it running the pi on full load for 18 hours a day.
 

Peter T

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Apr 6, 2018
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Ok, So the Pi been running for 10 Day's now, On 18 hours full load ( Running Dnet RC5 ). and 6 hours idle at midnight till 6am. On the old current Setup which is now 2 40W panel's , E-bay cheapo PWM charge controller, 12V 7ah SLA battery. And the Mopi connected to the Pi. Below is Voltage data from the MoPi.


image_pyhgmk.jpg
 

daromer

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Looks good!
Just beware not to cycle lead acid to low. They gets damaged pretty fast :)
 

Peter T

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Apr 6, 2018
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This is the current set-up on top of a toolbox. Just need to get some MDF to mount the 18650 battery holder's, Some fuse wire. And a BMS Then it be, 18650 Upgrade time. Side note I've had 2 weeks uptime on the Pi so far. But the weather been kind in the UK for the last two week's.


image_irqqnf.jpg
 

Peter T

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Apr 6, 2018
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Had a spare hour to start the next phase of my project. I still need to add a BMS. and test more cell's. And get up a ladder to set the panels up for 24V. But I'll get it done one day.

image_wxlbml.jpg
 

Peter T

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Apr 6, 2018
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Got myself one of those green MPT-7210A, so I can keep the twin 40watt 12V solar panel in parallel set-up going. with the 7s 2p 24V ( For now ! ), battery pack I've made up. Form my old battery's. The old 7Ah Lead acid done is job over the past two year's very well. My is somewhat modular so can get bigger when fund's/battery allow. Thank for Reading.
 

Peter T

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Apr 6, 2018
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Ok Update on my current set-up. 2 40 Watts panel's. One pointing North-East, one point South-West. These are in parallel with mpt-7210 solar controller, which is hooked up to a 7S 2P battery pack ( Yep Jehu's 18650 module ) . The other charge controller is use to give me the 5V out for the Raspberry Pi.


image_wvkiat.jpg
 

Crimp Daddy

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Feb 21, 2018
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Which standoffs are you using? Those look better than the brass ones.

I got some PCBs too, but I still need to get the rest of the parts so I can test it.
 

Peter T

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Apr 6, 2018
Messages
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One of the Sanyo cell's as turned into a heater. Still I have a few spare. I've also made a 3rd pack out of the 10 I have, Just need to find cell's in Sheffield UK.
 
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